Living in areas with high volumes of motorized traffic has been associated with respiratory symptoms and deceased lung function in children. Based on both these epidemiological findings and supporting experimental data, exposure to diesel-related air pollution has potential for health concerns that include asthma and allergy. However, despite substantial gains in our recognition of likely diesel-induced asthmatic or allergic symptoms, direct associations between exposure to diesel-related air pollution and the onset of atopy and asthma in young children have not yet been demonstrated. The interaction of diesel exposure with other urban exposures on respiratory health also is not clear. We hypothesize that exposure to diesel emissions in Northern Manhattan and the South Bronx is associated with allergen-specific sensitization, decreased lung function, and the onset of asthma in children at age 5 through 6 years. Our strategy is to take advantage of an established inner city birth cohort in which multiple environmental exposures and health outcomes already are being measured to evaluate whether exposure to diesel-related air pollution independently, or jointly with other prevalent urban environmental exposures (allergens, environmental tobacco smoke [ETS]), increase the risk for the onset of atopy or asthma. Specifically, we propose to use our established cohort to: Aim 1. Determine whether exposure to diesel-related air pollution is associated with the onset of allergen-specific sensitization, decreased lung function and/or asthma at age 5 through 6 years, and Aim 2. Determine whether exposure to diesel-related air pollution interacts with a) allergen, and/or b) ETS exposure, on the onset of allergen-specific sensitization, decreased lung function and/or asthma at age 5-6 years. 300 Dominican and African American children residing in Northern Manhattan that are being followed prospectively since birth as part of Columbia Center for Children's Environmental Health will be recruited at age 5 through 6 years. Two-week air monitoring at home for PAHs, black carbon, mass, and trace metals will be performed. Repeat measures of PM25 and carbon will be repeated 6 months later. Outcomes include sera IgE, antigen-specific T cell proliferation, allergy skin tests, lung function, and asthma diagnosis. The primary goals are to determine whether diesel-related exposure can induce the development of allergy and/or asthma, and to identify its contribution relative to other urban exposures.